Process for splitting hydrocarbons



Patented Oct. 22, 1929 UNITED s'rAras PATENT OFFICE OTTO SCHMIDT, OTTOGROSSKINSKY, AND GEOBG NIEMANN, OF LUDwIGSHAIB'EN-ON- THE-BHINE,GERMANY, ASSIGNORS TO I. G. FABBENINDUSTRIE AKTIENGESELL- BGHAI'I, OIrmxroa'r-on-rnnsm, GERMANY, A. CORPORATION 01! GERMANY PROCESS FORBPLITTING HYDBOCABBONB We hrawing. Application filed Kay 31, 1987,Serial No. 185,578, and in Germany June 19, 1926.

It is already known that hydrogenated aromatic hydrocarbons such forinstance as cyclohexane, tetrahydrobenzene and the like can be split byheatin the chief reaction. roda ucts thus obtaine being olefines andolefines, The operation has hitherto been performed in quartz vessels,or in the presence of quartz, platinum, charcoal or aluminium silicate.

We have now found that all kinds of h drocarbons having a highermolecular weig t than the desired products may be split, in a veryadvantageous manner, resulting in the lormation of olefines anddiolefines, by W bringing them into contact in the form of vapor at anelevated temperature, with contact masses which consist of or containone or more ditfioultly reducible metallic oxids.

Generally speaking those oxids and combina- W tions of several oxids,whether they are compounds or mixtures, which readily emit electronssuch as the known strontium oxid-barium oxid combinations either aloneor on a platinum substratum give the most favorable results. As is wellknown, the diflicultly reducible oxids of such elements as are situatedon the maxima of the curve of atomic volumes, or their dependentbranches, are particularly suitable for the emission of electrons.Hence, the oxids of the alkali metals or their hydroxids and salts,especially the aluminates, chromates, tungstates, vanadates, uranates,phosphates, and also alkaline-earth metal oxids such forexample as oxidsof calcium, strontium, barium, magnesium, glucinium or salts of thealkaline-earth metals, for example, aluminates, and also the oxids of.theelements scandium, titanium, yttrium, zirconium, lanthanum,tungsten, molybdenum, thorium and uranium, and the like, or mixtures ofthe same, or their compounds are suitable for use according to thepresent invention. The difficultly reducible oxids of the elements,which are situated on or near the minimaof the curve of atomic volume,such as aluminium, chromium and zinc are less suitable es ecially forthe production of butadiene by 0- carbons inasmuch as the effect. anextensive decomposition of the hy ocarbon molecules, though, on theother hand, they may be employed in the form of their salts, such asphosphates, chromates, vanadates and the like. Thus for example goodresults are obtained with aluminates of metals forming diflicultyreducible oxids, such as calcium, zinc, and the like, and also withother compounds of the dillicultly reducible metallic oxids with eachother, such as the vanadates,

chromates and tungstates of calcium, zinc and aluminium.

The said contact masses may be used either in the lump form, or may bedeposited on carriers, for which purpose carriers composed for exampleof the silicates of magnesium and aluminium are suitable. Metals mayalso be present in the contact masses, for exam is metals, such ascopper, platinum, molyb enum and tungsten, which have only a weakdehydrogenatlng action. When metals, such as iron, nickel and the likewhich have a powerful dehydrogenating action are used, they arebeneficial only it added in small quantities, but harmful if added inlarge amounts, because in the latter case they ellect extensivedecomposition of the hydrocarbons with the formation of carbon andhydrogen.

The employment of the hereinbefore described contact masses facilitatesthe formation of olefines and diolefines, and by their means it ispossible to obtain good yields of for example butadienes even fromcompletely hydrogenated benzene hydrocarbons. Other cyclic andnon-cyclic hydrocarbons may also be converted into olefines and the likewith good yields, by means-of the said catalysts. The employment of thesaid contact masses also enables the splitting temperature to be loweredin comparison with that hitherto in use for such processes, therebydiminishing the formation of carbon and improving'the yield in olefinesand diolefines.

The process according to the present invent-ion ma be applied bothtotheure'highmolecular ydrocarbons and to t eir mixtures, such as occur inRumanian, Galician,

Russian or American petroleum. It may even be applied for convertingbutylene into butadiene and lower olefines. It may be carried out underreduced pressure or in the presence or absence of other gases, such ashydrogen,

nitrogen, carbon dioxid, water vapor and the like and the operation maybe carrled on in a cycle by separating the unsaturated hydrocarbonsformed from the reaction mixture and passing the residual gases againover the contact mass. The temperature employed for the reaction shouldbe at least 500 0. and will generally range between about 550 and 750 0.The most suitable temperature depends on the nature of the catalyst thekind of initial material and on the desired product. Good yields ofethylene hydrocarbons and butadienes may be produced in a simple manneraccording to the said process from readily and cheaply available initialmaterials and the process is therefore of high industrial im ortance.

he following examples will further illustrate how the said invention maybe carried into practical effect, but the invention is not limited tothese examples.

Example 1 Tetrahydrobenzene vapor is passed through a contact furnace,constructed of inert mate-- rials, for example of porcelain, clay, noblemetals, or other metals not giving rise to deposition of carbon andcharged with coarse lumps of calcium oxid, at a temperature of 625 0.and at such velocity that about 30 per cent of the tetrahydrobenzene issplit up. The gases issuing from the furnace are fractionally cooled, orexample by passing them first through an ice-cooled receiver, and thenthrough one cooled with a mixture of toluene and solid carbon dioxid.The bulk of the unaltered tetrahydrobenzene separates out in the firstreceiver, whilst butadiene, besides propylene, butylene and theremainder of the tetra ydrobenzene and small amounts of imurities arecollected in the second receiver. e gaseous constituents formed consistchiefly of ethylene, methane and hydrogen. In most cases the gasesleaving the second receiver contain further considerable amounts ofbutadienes which may be recovered by stronger coolin Instead ofseparating the butadines mere y by cooling, they mayalso be recovered bycompression with or without cooling; the yield of crude butadienesamounts then to about 85 per cent of the theoretical, whilst that ofethylene is a proximately quantitative. The unaltere tetrahydrobenzeneis preferably used over again, after having, if necessary, been purifiedby fractional distillation.

Example 0 Hexahydrobenzene is passed, at about 600 0., through a contactapparatus constructed of, or lined with, quartz or clay and charged withcalcium aluminate moulded into the shape of cubes, the rate of flowbeing such that about 40 per cent of the hexahydrobenzone is split up.The principal decomposition products obtained are ethiylene andbutadiene which are separate speci ed in Example 1. The yield ofbutadienes is good, and that of ethylene approximately quantitative.

' Example 3 roducts contain a large proportion of olenes.

In the foregoing exam les the catalysts mentioned may be replace byother contact masses of the kind specified, and both the temperature andrate of flow may also be modified. The hydrocarbon vapors may also be'used in association with other gases, such as hydrogen, nitrogen, carbondioxid, water vapor and the like.

Example 4 A mixture of 1 part, by volume, of betabutylene (boiling point1 0.) and at least 5 parts, by volume, of nitrogen is passed at 700 0.over coarse granules of strontium uranate, at a rate of about 10 gramsof butyl- 1 ene per hour and per square centimetre of thecross-sectional area of the contact vessel. Hydrogen is s lit off and agood yield of butadiene besi es unaltered initial material is obtained.The reaction may also be carried out under reduced pressure without theaddition of nitrogen or other gases.

What we claim is:

1. The process of splitting hydrocarbons having a higher molecularweight than the desired products to olefines and diolefines whichconsists in bringing the hydrocarbon vapors into contact, attemperatures above 500 0., with a contact mass comprising a difiicultlyreducible metal oxid. I

2. The process of splitting hydrocarbons having a igher molecular weightthan the desired products to olefines and diolefines which consists inbringing the hydrocarbon vapors into contact, at temperatures above 5000., with a contact mass comprising a difiicultly reducible metal oxidcapable of readily emitting electrons.

3. The process of splitting hydrocarbons having a igher molecular weightthan the desired products to olefines and diolefines which consists inbringing the hydrocarbon vapors into contact, at temperatures betweenabout 550 and 750 0., with a contact mass comprising a difiicultlyreducible metal oxid.

in the manner a 4. The recess of splitting hydrocarbons having a ighermolecular Weight than the desired products to olefines and diolefineswhich consists in bringing the hydrocarbon vapors into contact, attemperatures above 500 (1, with a contact mass comprising an alkalineearth metal oxid.

In testimony whereof We have hereunto set our hands.

OTTO SCHMIDT. OTTQ GROSSKINSKY GrEURGr NIEMANN.

